RXR agonist bexarotene modulates the cell‐fate and migration abilities of adult neural stem cells in vitro

Background Targeting the nuclear RXR receptors has been associated with brain‐specific roles with striking therapeutic potential for Alzheimer’s Disease (AD), with similar observations to its dimerization partners such as LXR and PPAR whose responses are also under influence of RXR activation. Treatment with bexarotene, a selective RXR agonist, leads to significant recovery of cognitive loss in variable mice AD‐like models ‐ and also activates neurodevelopment and plasticity pathways in adult mice brains. Our hypothesis is that neural stem cells (NSC) residing in the adult brain directly respond to bexarotene, leading to improved neurogenesis and other effects compatible with brain recovery. Method We employed an in vitro strategy using NSCs isolated from the subventricular zone of adult rats’ brains. Adult NCSs were treated with bexarotene from neurosphere proliferative stage to differentiated states, and the cell‐fate consequences were evaluated through morphometric analysis and immunofluorescence of cell markers. Result In proliferative stages, bexarotene‐treated adult NSCs exhibited increased cell outgrowth from neurospheres. Bexarotene treatment also led to changes in the cell fate of differentiating cells, with a marked increase in GFAP staining after differentiation. Relatively to newborn neurons, we found a decrease in DCX positive staining of neuroblasts after bexarotene treatment. However, Tuj1 staining of neurons was preserved. Neurite number, length, and bifurcations in differentiated neurons were unaffected by bexarotene. Conclusion Adult NSCs respond to bexarotene by increasing migration abilities and generating more GFAP+ cells. Results indicate that RXR activation by bexarotene in adult NSCs preserves, but does not activate, neuronal differentiation and neurite complexity. The significance of the increased GFAP+ glial cell population, as well as the decreased DCX+ young neurons, remains to be unrevealed. Finally, we did not observe clear bexarotene‐induced changes in neurosphere proliferation, but the effect of RXR activation over pluripotency in these cells needs further investigation. These findings address a gap in our knowledge regarding the brain effects of bexarotene, substantiating the search and possible application of RXR‐based approaches to AD.